Multi-core smartphones already become a new trend in the mobile phone market. At present, relatively prevailing smartphones have 4 cores, and in the future, smartphones with 8 cores or even more cores will come out. Because a multi-core smartphone supports functions such as network access, movie and television, and entertainments, a user spends much more time in using a multi-core smartphone than using a single-function mobile phone. Accordingly, power consumption of the multi-core mobile phone may gradually increase, so that battery power of the multi-core mobile phone may be easily exhausted during use.
Generally, a mobile phone is charged by using a dedicated charger. However, the mobile phone may also be charged by a laptop computer through a USB (Universal Serial Bus, universal serial bus) interface. According to charging specifications for a USB2.0 interface, when a USB interface is not in a suspended state, a USB interface of a laptop computer may supply a 100 mA current to a device as long as the device is connected to the laptop computer through the USB interface. Generally, a user hopes that a mobile phone can support a charging scenario: When the mobile phone is in a power-off state due to low power, the mobile phone is connected to a laptop computer through a USB and the laptop computer supplies power to the mobile phone, so that the mobile phone can normally start during charging.
For the foregoing charging scenario, the prior art provides the following solutions:
In solution 1, as shown in FIG. 1A, a starting procedure of a mobile phone after being powered on includes the following steps:                {circle around (1)} Run a boot program in an on-chip read only memory, so as to read a bootloader program from an off-chip flash memory and load the bootloader program to an on-chip random memory.        {circle around (2)} Run the bootloader program in the on-chip random memory to initialize an off-chip random memory.        {circle around (3)} Run the bootloader program in the on-chip random memory, so as to read a system mirror from the off-chip flash memory, for example, a mainstream Android mirror, and load the system mirror to the off-chip random memory.        {circle around (4)} Run the system mirror in the off-chip random memory.        
In the foregoing starting procedure, peripheral devices such as a Timer, a UART, and an LCD may also be used. A USB is used only when the system mirror runs and the mobile phone is already in a power-on state.
This solution has the following disadvantages:
Because, in a process of reading the system mirror from the off-chip flash memory to the off -chip random memory, both the off-chip flash memory and the off-chip random memory need to be accessed, power consumption of the mobile phone may be high. However, a 100 mA current supplied by the USB interface of the laptop computer generally cannot satisfy the power consumption of the mobile phone. Therefore, when a charging current of 100 mA from the USB cannot meet a power consumption demand of the mobile phone, the startup process of the mobile phone cannot be completed by using the current supplied by the USB. As a result, the mobile phone fails to start, thereby affecting use of the user.
In solution 2, as shown in FIG. 1B, a starting procedure of a mobile phone after being powered on includes the following steps:                {circle around (1)} Run a boot program in an on-chip read only memory, so as to read a bootloader program from an off-chip flash memory and load the Bootloader program to an on-chip random memory.        {circle around (2)} Run the bootloader program in the on-chip random memory to initialize an off-chip random memory.        {circle around (3)} Run the bootloader program in the on-chip random memory to control a coulomb meter to query power, wait, when it is queried that the battery power is lower than a starting threshold, until the battery power after charging satisfies the starting threshold, and perform the following step {circle around (4)}.        {circle around (4)} Run the bootloader program in the on-chip random memory, so as to read a system mirror from an off-chip flash memory, for example, a mainstream Android mirror, and load the system mirror to the off-chip random memory.        {circle around (5)} Run the system mirror in the off-chip random memory.        
This solution has the following disadvantages:
In step {circle around (3)}, because the laptop computer supplies a current of 100 mA to charge the mobile phone, there exists a problem that a charging process is slow and charging waiting time is long. In addition, in the solution, the mobile phone can be started up for use only after the battery power is charged to reach a starting threshold. In a charging waiting process, the mobile phone cannot be started up, low power in the mobile phone cannot support display on an LCD, and the user cannot know whether the mobile phone has entered the charging process and cannot know a current battery power value.